It is often desirable for rail road cars to weigh out at the same time as they bulk out. For example, the maximum gross weight on rail of a “110 Ton” railroad freight car in North America is 286,000 lbs. If the car carries less than the maximum allowed lading by weight, then an unnecessarily high proportion of the weight being hauled is the weight of the car itself—which is also backhauled empty. Therefore, it follows that most often when relatively low density lading is to be carried it is desirable to have a high volume. This reflects conventional understanding in the railroad industry. Municipal waste tends to provide an example of relatively low density lading. Wood chips may provide another example.
It may be desirable to increase the size of the car by making the car taller. However, a fully laden car must not have a center of gravity more than 98 inches above top of rail (TOR). Therefore, is may also be desirable to extend the lading carrying envelope downward, below the upper flange (or top cover plate) of the center sill, below the height of the center of the couplers, and even below the bottom flange (or bottom cover plate) of the center sill. For this purpose a designer might consider the “bathtub” feature, of which the classic example is the bathtub gondola car shown and described in U.S. Pat. No. 4,361,097 of Jones et al., issued Nov. 30, 1982. As the walls of the gondola increase in height, there may not only be a center of gravity concern, but also a concern that the sidewalls of the car may begin to lack adequate side-ways stiffness. This may be particularly so where the car is to be emptied in a rotary dumping apparatus and where the length of the car has also been increased, with the truck centers being spaced more than, and possibly quite substantially more than, 46′-3″ apart. Finally, it may be desired partially to compress the lading in the car. That is, in one example, it may be desired partially to compact municipal waste in the car as it is loaded.